1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to an apparatus for coating photoresist capable of preventing photoresist, which is introduced into a drain pipe when photoresist is coated on an upper surface of a substrate formed with devices, from flowing backward, thereby preventing a rear surface of the semiconductor substrate, which is opposite to the upper surface formed with devices, from being contaminated.
2. Description of the Prior Art
Generally, in order to fabricate IC semiconductor devices, liquid crystal display devices, and plasma display devices, it is necessary to form a predetermined material pattern on a semiconductor substrate (wafer) or a glass substrate. To this end, after coating photoresist on an entire upper surface of a material layer formed on the semiconductor substrate or the glass substrate, the photoresist is exposed and developed, thereby forming a photoresist pattern. Then, the material layer is etched by using the photoresist pattern as a mask, thereby forming a material layer pattern. A photoresist coating apparatus is used for coating the photoresist on the semiconductor substrate or the glass substrate. Hereinafter, a conventional photoresist coating apparatus will be described with reference to FIG. 1.
FIG. 1 is a schematic sectional view of a conventional photoresist coating apparatus.
As shown in FIG. 1, the conventional photoresist coating apparatus includes a vacuum chuck 15 capable of gripping a substrate 13, such as a semiconductor substrate or a glass substrate, by using vacuum, a driving motor 19 connected to the vacuum chuck 15 through an arm 17 in order to rotate the substrate 13 at a high speed, a first nozzle 23 installed above the vacuum chuck 15 in order to coat photoresist 21 onto the substrate 13, a second nozzle 25 installed below the vacuum chuck 15 in order to perform a rinse process with respect to a rear surface of the substrate 13, and a bath 11 surrounding the vacuum chuck 15 including the substrate 13 in order to prevent photoresist 21 which has fallen down from the substrate 13 from being discharged to an exterior.
When performing the photoresist coating process by using the conventional photoresist coating apparatus having the above construction, the substrate 13 is firstly loaded on the vacuum chuck 15. Then, photoresist 21 is coated on a surface of the substrate 13 through the first nozzle 23. At this time, since the vacuum chuck 15 is formed with a plurality of fine vacuum holes (not shown), vacuum force is applied to the substrate 13 through the fine vacuum holes when photoresist 21 is coated on the upper surface of the substrate, so that the substrate 13 is fixedly maintained on the vacuum chuck 15.
After that, the substrate 13 loaded on the vacuum chuck 15 is rotated at a predetermined speed by using the driving motor 19 and the arm 17, so that photoresist 21 is evenly coated on the upper surface of the substrate 13 due to centrifugal force applied thereto. At this time, since a lower end portion of the bath 11 is connected to an exhaust pipe (not shown), photoresist contained in the bath 11 is exhausted to an exterior through the exhaust pipe.
In addition, a rinsing solution is fed to the rear surface of the substrate through the second nozzle 25, so photoresist which has dropped from the upper surface of the substrate 13 and attached to the rear surface of the substrate 13 due to the rotation of the vacuum chuck 15 can be removed from the rear surface of the substrate 13.
FIGS. 2 and 3 are photographic views representing problems of prior arts. FIG. 2 shows an annular pattern formed at the rear surface of the substrate, and FIG. 3 shows a pattern bridge phenomenon created in the substrate.
When the vacuum chuck is rotated at a high speed after photoresist has been coated on the substrate, photoresist including volatile component must be exhausted to the exterior through the drain pipe connected to the lower end portion of the bath. However, according to the prior art, a swirl flow is created due to high-speed rotation and vacuum characteristics, so photoresist introduced into the drain pipe is not exhausted to the exterior, but flows backward so that photoresist is attached to a predetermined portion of the substrate, that is, attached to the rear surface of the substrate, thereby contaminating the rear surface of the substrate. The photoresist attached to the rear surface of the substrate may act as a contamination source, causing defects in the substrate. Such defect may include an annular pattern formed around a vacuum hole as shown in FIG. 2.
Therefore, when an exposure process is carried out with respect to the substrate by moving the substrate having the contaminated rear surface into a stage of exposure equipment, the stage may be contaminated, so that a focus error is generated when forming a pattern on the substrate. Thus, as shown in FIG. 3, a pattern bridge phenomenon may occur in the substrate, causing defects in the substrate.